1. Field of the Invention
The present invention relates to a method for cleaning the interior of a molding machine including a residual thermoplastic resin after molding the same as well as a cleaning composition for cleaning the molding machine and more specifically, to a method for cleaning the interior of a molding machine in which a resin remains after a molding operation, which makes it possible to immediately change the kinds and colors of resins within a single molding machine and to improve the quality of products and production efficiency.
2. Prior Art
General purpose thermoplastic resins such as styrenic resins and olefinic resins as well as engineering plastics have widely been used in various fields because of their excellent physical properties. These thermoplastic resins have been variously colored and formed into a variety of shapes by manufacturers and processors. The manufacturers and processors have frequently changed the kinds and colors of resin in a single molding machine in accordance with the recent diversity in market needs. Such changes in the kinds and colors of resin result in a waste of time and materials and correspondingly, there has been desired the development of a method for effective cleaning of the interior of a molding machine in order to improve production efficiency and quality of the resulting products.
Under such circumstances, there have already been proposed some cleaning agents. For instance, Japanese Unexamined Patent Publication (hereinafter referred to as "J. P. KOKAI") No. Hei 2-308899 discloses a cleaning agent comprising a thermoplastic resin in which 0.5 to 25% by weight of water is incorporated. Further, J. P. KOKAI Nos. Sho 58-149998, Sho 59-124999 and Sho 60-139411 propose cleaning agents comprising inorganic fillers.
These cleaning agents are effective for the removal of resins remaining in a molding machine, but the cleaning agents per se are liable to remain in the machine, correspondingly a great deal of time and a large amount of materials are required for substituting an intended resin for the cleaning agents and thus these cleaning agents are insufficient for achieving the foregoing purposes. Moreover, they are effective only for specific thermoplastic resins and do not have universality in the cleaning effect. In other words, they are limited in their applications.
In addition, there have been proposed cleaning agents which comprise thermoplastic resins and surfactants in J. P. KOKAI Nos. Sho 62-195045 and Hei 3-74499 and a cleaning agent which comprises a styrenic resin and a polyalkylene oxide glycol in J. P. KOKAI No. Hei 2-163144.
These cleaning agents can solve the foregoing problem of limited applications, but still suffer from the problem that the cleaning agents per se remain in the interior of molding machines.